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Quantum Communication Quantum Communication: QKD, teleportation into a solid-state quantum memory and Large entanglement Nicolas Gisin, Hugo Zbinden, Mikael Afzelius, Rob Thew and Félix Bussières GAP-Optique, University of Geneva . Commercial QKD system . Why QKD ? . Longer distances: networks based on trusted nodes Geneva University . Q memories for quantum repeaters and networks . Large Entanglement GAP Quantique GAP 1 Years of continuous commercial operation 75 km Installed multiplexed quantum channel for commercial users. Geneva University GAP Quantique GAP Used daily by some commercial 2 t Why QKD ? How much of a problem for QKD is quantum Geneva University computing, really?? GAP Quantique GAP Courtesy of Prof. Michele Mosca3 How soon do we need to worry? Depends on: . How long do you need encryption to be secure? (x years) . How much time will it take to re-tool the existing infrastructure with large-scale quantum-safe solution? (y years) . How long will it take for a large-scale quantum computer to be built (or for any other relevant advance? (z years) Theorem 1: If x + y > z, then worry. Geneva University What do we do here?? y x z GAP Quantique GAP time Courtesy of Prof. Michele Mosca GAP Quantique Geneva University Courtesy of Prof. Michele Mosca Michele of Prof. Courtesy 5 How far can one send a photon ? Secret Rate Key P2P + WDM Rate 10MHz +4 Years 1MHz Today Lab Today Commercial 100kHz 10kHz 1kHz Geneva University 1Hz 100 200 300 400 Distance [km] There is a hard wall around 400 km ! With the best optical fibers, perfect noise-free detectors and ideal 10 GHz GAP Quantique GAP single-photon sources, it would take centuries to send 1 qubit over 1000 km ! 6 Long distance QKD: World records 150 km of installed fibers, Optics Express 17, 13326 (2009) Lausanne 250 km in the lab. NJP 11, 075003 (2009) Geneva University GAP Quantique GAP 7 Proposals for quantum communication in space Dual-downlink Single-uplink (ROM R&D 47 M€) (ROM R&D 1 M€) Astronaut: Using a motorized A. Kuipers photo-lens-pod (existing) and a dedicated quantum detector as “camera”. Geneva University Simultaneous optical downlink: 1400 km separation. GAP Quantique GAP R. Ursin et al., Europhysics News, T. Scheidl, E. Wille, and R. Ursin, 26-29, 40–40 (3) (2009) New Journal of Physics, 15, 043008 (2013) [email protected] - Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences Network-centric Quantum Communications Richard Hughes, Jane Nordholt and team Los Alamos National Laboratory application layer: • confidentiality • authenticity • integrity • non-repudiation • between users who may have no direct QC quantum key management (QKM) layer: • classical protocols built from quantum primitives • key establishment • signatures • certificates quantum protocol layer: Geneva University • quantum identification (QID) • quantum key distribution (QKD) • quantum secret splitting (QSS) quantum physical layer: • novel BB84-type QC in fiber • quantum multiple access (QMA) GAP Quantique GAP • quantum random number gen. R. J. Hughes et al., US Patent 8,483,394; US Patent Applications: US 20130083926 A1; US2013/055356 R. J. Hughes et al., J. E. Nordholt, et al., US Patent Applications: 61/693,131, US20130101119 A1, US 20130084079 A1, US2013/055430 arXiv:1305.0305 Long Range QKD with trusted nodes Battelle QKD Backbone • Columbus OH to Washington DC Area • > 770 km • Deployment targeted in 2015 800 km Geneva University Battelle Aberdeen Office GAP Quantique GAP Battelle Main Campus Courtesy Dr Don Hayford The Security Onion Battelle Environment Physical Protection Enclosure Access Control Chassis Geneva University Security Protocols Intrusion Detection Cryptographic Boundary GAP Quantique GAP N-photon quantum communication: quantum networks, quantum internet Q repeaters Geneva University We still miss the capability to store entanglement: Developing quantum memories is a grand challenge ! GAP Quantique GAP 12 Quantum memory Goal: controlled and reversible mapping of a photonic quantum state onto a long lived atomic ensemb crystal doped with billions of photon out photon in ions at desired time in same Q state The quantum state of the photon Today’s efficiencies Geneva University is now coded in a huge entangled states of billions 20of «% atoms » Nature 456, 773, 2008 GAP Quantique GAP 13 Controlling the Dephasing! Atomic Frequency Comb N ikr i t e j e j g ...e ...g i jt 1 j N Pj e j1 Δ continuous Dephasing Im(Pj ) Re(Pj ) Absorption Frequency Geneva University Δ periodic Rephasing Im(Pj ) Re(Pj ) Absorption GAP Quantique GAP Frequency Rephasing after 14 k mk , mk 0,1,2,... T 1 Atomic Frequency Comb (AFC) Quantum Memory Periodic! AFC preparation 2 levels: preprogrammed Photon Control delay (AFC echo) Echo 3 levels: on-demand re- emission (spin wave storage) Geneva University Signal Preparation Photon Echo Echo GAP Quantique GAP Time M. Afzelius et al. PRA 79, 052329 (2009) AFC echo 3.0 (a) 2.5 100 2.0 25 input d 1.5 80 1.0 20 Optical depth Optical 0.5 d 0.0 0 60 0 102030405060708090100 15 transmitted Optical detuning [MHz] 40 10 Geneva University 20 echo 5 Normalized intensity (arb. units) 0 0 012345 Time (s) GAP Quantique GAP 16 3+ Multi-mode storage in Nd :Y2SiO5 Mapping 64 input modes onto one crystal n < 1 per mode 1.0 Input modes Output modes x50 0.8 0.6 0.4 0.2 Normalized counts Normalized 0.0 0.0 0.4 0.8 1.2 1.6 2.0 2.4 64 time modes can be usedTime to (s) code 32 time-bin qubits! Input mode 1.0 Output mode x50 0.8 0.6 0.4 0.2 normalized counts 0.0 Geneva University 0.0 0.5 1.0 1.5 2.0 2.5 time [s] Input mode 1.0 Output mode x50 0.8 0.6 0.4 0.2 normalized counts GAP Quantique GAP 0.0 0.0 0.5 1.0 1.5 2.0 2.5 time [s] I. Usmani et al., Nature Communications 1,12 (2010) 17 Entanglement‐preserving quantum memory H H V V 1338HH 883 VV 1338 883 Geneva University Bandwidth: 680 MHz GAP Quantique GAP to Quantum Memory then to measurement device Entanglement‐preserving quantum memory Geneva University GAP Quantique GAP Entanglement‐preserving quantum memory H H V V 1338HH 883 VV 1338 883 Using Bell test as Entanglement Witness Magnet D1 D2 Magnet Geneva University GAP Quantique GAP S larger than local bound of 2 Device-Independent Entanglement! C. Clausen, F. Bussières, A. Tiranov, M. Afzelius et. al. arXiv:1401.6958 Geneva University sspd from NIST GAP Quantique GAP Quantum teleportation of a telecom-wavelength photon to a solid-state quantum memory Partial Bell State Measurement and post-selected fidelity F. Bussières, Ch.Clausen et al., arXiv:1401.6958 Tomographic reconstruction (short link) Analysis on a great circle of the Poincaré sphere Geneva University Fidelity of teleportation (2x12.4 km) GAP Quantique GAP What do we need to do the full AFC memory scheme? Input Control Pulses Output Zeeman or hyperfine states Geneva University Signal Preparation Photon Echo Echo GAP Quantique GAP Time 151 3+ Some Basic Eu :Y2SiO5 Spectroscopy 5/2 102 MHz 5 D0 3/2 75 MHz 1/2 Inhomogeneous absorption spectrum (100 ppm 153Eu) Control Pulses 580 nm 0.8 Geneva University 0.6 1/2 35 MHz 7 3/2 0.4 F0 5/2 46 MHz Transmitted intensity 700 MHz 0.2 d=1.3 0 -2000 -1000 0 1000 2000 Frequency (MHz) GAP Quantique GAP -Excited state life time 2 ms -1 N. Timoney, I. Usmani, P. Jobez, MA, N. Gisin, arXiv:1301.6924 - Max. absorption coefficient 3-4 cm PRA 88, 02324 (2013) - Spin coherence time 15 ms for 151Eu (B=0) Towards high SNR and long‐lived Quantum Memory Work in progress… 1. Higher two-level AFC 2. Higher two-level AFC efficiencyy Method 1 efficiencyy Method 2 Frequency stable laser, optimized comb preparation 1 Cavity enhanced QM 0.8 Afzelius & Simon 1000 49% 0.6 PRA 82, 022310 Intensity 0.4 (2010) Intensity 500 11.5% 0.2 0 0 5 10 0 -0.2 -0.1 0 0.1 0.2 Time, s 1/ (s) 3. Longer two-level AFC storage time 4. Milliseconds spin-wave storage Geneva University Frequency stable laser time Spin-echo techniques 50 ms GAP Quantique GAP 3. Large Entanglement Natalia Bruno, Anthony Martin, Pavel Sekatski, Nicolas Sangouard, Rob Thew and Nicolas Gisin Group of Applied Physics Geneva University, Switzerland Geneva University GAP Quantique GAP 26 Do these entangled crystals count as macroscopic entanglement ? Nature Photonics 6, 234-7, 2012 Geneva University GAP Quantique GAP 27 What is macroscopic ? What is quantum ? . Do these 2 crystals count as large entanglement? No ! . Billions of ions in a macroscopic object, but “only” one Geneva University -delocalized -excitation . Quantum = entanglement. Nature Photonics 6, 234-7, 2012 GAP Quantique GAP 28 Example: 1-photon entanglement . 1-. BS . 0,1 1,0 Geneva University GAP Quantique GAP 29 Example: displaced 1- entanglement . 1-. BS . _ |2. D() 1 D() 1 Geneva University The components of this entangled state can easily be distinguished using classical detectors because nD( ) 1 3n GAP Quantique GAP Pavel Sekatski, Nicolas Sangouard et al., PRA 86, 060301 (2012) 30 Distinguishability |0D()|1+|1| =|+-+|-+ Photon number distribution Where = D()|1| Geneva University For ||2>>, Pguess 74%For ||2>>, Pguess 89% GAP Quantique GAP Pavel Sekatski, Nicolas Sangouard et al., PRA 86, 060301 (2012) 31 Toward truly Large Entanglement ...... Quantum memories 1-’s BS ...... ...... .... |2’s . j j D() 1j D() 1j j Geneva University Inside the crystal, no longer a product state, But a complex sort of Dicke state with involved Phase relations.
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